The plot sounded gruesome — and difficult to pull off: Drive behind the White House. Create a diversion. Use an explosive to blow a hole in the highly guarded building. Then storm inside and shed the blood of as many people as possible.

But first, Hasher Jallel Taheb wanted to do a little sight-seeing in D.C., according to FBI documents.

Unrealistic as it all seemed, experts say he still could’ve been dangerous.

The 21-year-old Forsyth County man was arrested Wednesday in Gwinnett County while allegedly exchanging his vehicle for weapons to attack the White House, possibly as soon as today. Taheb gave details of his plan to two people he thought were helping him obtain explosives and firearms but were really an FBI informant and undercover agent, according to a criminal complaint filed in federal court. He was charged with plotting to destroy a government building after a months-long investigation.

Authorities haven’t connected Taheb with any known terrorist group. Still, his case highlights the continuing danger of so-called “homegrown” suspects who become radicalized online, several counter-terrorism experts say. Taheb was allegedly inspired by the teachings of the late Yemeni-American imam Anwar al-Awlaki, though the information released so far suggests he was poorly prepared to carry out his plan.

For instance, authorities said Taheb told the undercover agent just days ago that he’d still never fired a gun or used explosives, but could learn quickly. He also told an informant of plans to travel to Islamic State territory, though he acknowledged he had no passport.

However ill prepared he was, the intent detailed in the criminal complaint is troubling, said Georgia Tech professor Margaret Kosal, who has long studied terrorism and advised the federal government on defense issues.

“In the course of trying to get to accomplish a fantastical plot, somebody can get hurt,” Kosal told The Atlanta Journal-Constitution. “The FBI is forced to take all of them seriously, and that is what they should do.”

Few details have emerged about Taheb, other than he lived south of Cumming with his mother and had attended schools in both Forsyth and Gwinnett counties in recent years. Gwinnett County school officials wouldn’t reveal which school he’d last attended. In 2013, he transferred to Forsyth Central High and graduated two years later, officials said.

His family hasn’t returned phone calls, and it’s unknown if he has a lawyer yet.

Taheb, who remains in federal custody, has no known prior arrest history. He came on law enforcement radar when a resident sent a tip about him to the FBI last January. Authorities wouldn’t go into detail about that tip. They say another tip came to the Forsyth County Sheriff’s Office in March, when a resident said Taheb had become radicalized and was making plans to travel abroad. When the 21-year-old put his vehicle up for sale in August to fund a trip to Islamic State territory, an FBI informant reached out to show interest. Taheb told the potential buyer about his intentions, according to the complaint.

Cumming man threatened to attack White House, authorities say

The informant and an undercover FBI agent spoke with him for months as he expressed intent to attack the White House, Lincoln Memorial and Washington Monument with IEDs, anti-tank weapons and guns, the complaint said.

It appears that Taheb’s goals exceeded his capabilities, and that’s a good thing, said Seth Jones, a senior adviser at the Center for Strategic and International Studies.

Had Taheb’s plan been simpler, Jones said, the result might’ve been more like the Pulse nightclub massacre in Orlando instead of an FBI sting operation. “In this country, it does not require a lot to conduct a terrorist attack,” Jones said. Weapons can be obtained easily and, as recent Western attacks have reminded, vehicles can be used to kill in crowds.

In sting operations like the one that took down Taheb, defense attorneys often accuse authorities of entrapment, of goading the defendants into going farther than they would have alone. But experts say the complaint appears to show a troubling intent on Taheb’s part.